Drs. Allen Breier and Andred de Bartolomes are interested in using PET and 11C-Raclopride to study the displacement of 11C-Raclopride in schizophrenic patients and healthy controls. The purpose of the study is to examine dopamine function using displacement of 11C-Raclopride by methylphenidate induced increases in synaptic dopamine. The specific aims are to develop a method for determining estimates of in vivo synaptic dopamine concentrations in humans, and to utilize this method to test the hypothesis that schizophrenia is associated with increased methylphenidate-induced dopamine release. The objective of this project was to synthesize Raclopride labeled with carbon-11, a cyclotron produced, positron-emitting radionuclide, which will permit imaging the brain using positron emission tomography (PET). We have synthesized 11C-Raclopride in sufficient radiochemical yields and purities for human studies. The amounts of product and specific activities of 11C-Raclopride at high irradiation levels are presently being determined.